Three-dimensional semiconductor memory device

ABSTRACT

According to one embodiment, a semiconductor memory device includes a substrate; an insulating layer provided on the substrate; a conductive layer provided on the insulating layer; a stacked body provided on the conductive layer and including a plurality of electrode layers and a plurality of insulating layers respectively provided among the plurality of electrode layers; a columnar section piercing through the stacked body to reach the conductive layer and extending in a first direction in which the stacked body is stacked; and a source layer. The columnar section includes a channel body and a charge storage film provided between the channel body and the respective electrode layers. The conductive layer includes a first film having electric conductivity and in contact with the lower end portion of the channel body; and an air gap provided to be covered by the first film.

This application is a continuation of U.S. application Ser. No.15/344,021 filed Nov. 4, 2016, which is a continuation of U.S.application Ser. No. 14/597,580 filed Jan. 15, 2015, and is based uponand claims the benefit of priority from U.S. Provisional PatentApplication 62/047,369 filed on Sep. 8, 2014; the entire contents ofeach of which are incorporated herein by reference.

FIELD

Embodiments described herein relate generally to a semiconductor memorydevice and a method for manufacturing same.

BACKGROUND

A memory device having a three-dimensional structure has been proposedin which a memory hole is formed in a stacked body formed by stacking aplurality of electrode layers, which function as control gates in memorycells, via insulating layers and a silicon body, which functions as achannel, is provided on a sidewall of the memory hole via a chargestorage film.

According to refining of the memory cells, it is likely thatdeterioration in reliability of the memory cells is caused. Further,contact formation of the channel could be difficult.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a schematic perspective view of a memory cell array in anembodiment;

FIG. 2A is a schematic sectional view of the memory strings in theembodiment and FIG. 2B is a schematic top view of the memory strings inthe embodiment;

FIG. 3 is an enlarged schematic sectional view of a part of the columnarsection of the embodiment;

FIG. 4A to FIG. 13B are schematic views showing a method formanufacturing the semiconductor memory device of the embodiment;

FIG. 14A is a schematic top view of the memory strings in anotherembodiment and FIG. 14B is a schematic;

FIG. 15A and FIG. 15B are schematic views showing a method formanufacturing the semiconductor memory device of the another embodiment;

FIG. 16A is schematic top view of the memory strings in still anotherembodiment and FIG. 16B is schematic sectional view of the memorystrings in the still another embodiment;

FIG. 17A and FIG. 17B are schematic views showing a method formanufacturing the semiconductor memory device of the still anotherembodiment;

FIG. 18 is an enlarged schematic sectional view of a part of a columnarsection in another memory cell array in the embodiment; and

FIG. 19 to FIG. 23 are schematic sectional views showing a method formanufacturing the other memory cell array in the embodiment.

DETAILED DESCRIPTION

According to one embodiment, a semiconductor memory device includes asubstrate; an insulating layer provided on the substrate; a conductivelayer provided on the insulating layer; a stacked body provided on theconductive layer and including a plurality of electrode layers and aplurality of insulating layers respectively provided among the pluralityof electrode layers; a columnar section piercing through the stackedbody to reach the conductive layer and extending in a first direction inwhich the stacked body is stacked; and a source layer piercing throughthe stacked body to reach the conductive layer and extending in thefirst direction and a second direction that crosses the first direction.The columnar section includes a channel body including a lower endportion projecting into the conductive layer, electrically connected tothe source layer via the conductive layer, and extending in the firstdirection; and a charge storage film provided between the channel bodyand the respective electrode layers. The conductive layer includes afirst film having electric conductivity and in contact with the lowerend portion of the channel body; and an air gap provided to be coveredby the first film.

Embodiments are described below with reference to the drawings. Notethat, in the drawings, the same elements are denoted by the samereference numerals and signs.

FIG. 1 is a schematic perspective view of a memory cell array 1 in anembodiment. Note that, in FIG. 1, insulating layer and the like are notshown to clearly show the figure.

In FIG. 1, two directions parallel to a major surface of a substrate 10and orthogonal to each other are referred to as X-direction andY-direction. A direction perpendicular to both of the X-direction andthe Y-direction is referred to as Z-direction (stacking direction).

The memory cell array 1 includes a plurality of memory strings MS.

FIG. 2A is a schematic sectional view of the memory strings MS. FIG. 2Ashows a cross section parallel to a YZ plane in FIG. 1.

FIG. 2B is a schematic top view of the memory strings MS. FIG. 2B showsa top surface parallel to an XY plane in FIG. 1.

A source side selection gate SGS is provided on the substrate 10 viaconductive layer 60. An insulating layer is provided on the source sideselection gate SGS. A stacked body 15 in which a plurality of electrodelayers WL and a plurality of interlayer insulating layers 40 arealternately stacked one by one is provided on the insulating layer. Notethat the number of the electrode layers WL shown in the figure is anexample. The number of the electrode layers WL may be any number. Forexample, the plurality of electrode layers WL is stacked and separatedfrom each other. The plurality of interlayer insulating layers 40includes an air gap.

The interlayer insulating layer 40 is provided on the top electrodelayer WL. A drain side selection gate SGD is provided on the insulatinglayer.

The source side selection gate SGS, the drain side selection gate SGD,and the electrode layers WL are, for example, silicon layers includingsilicon as a main component. For example, boron is doped in the siliconlayers as impurities for giving electric conductivity. The source sideselection gate SGS, the drain side selection gate SGD, and the electrodelayers WL may include at least one of metal or metal silicide. As theinterlayer insulating layer 40, for example, insulating film mainlyincluding silicon oxide is used.

The thickness of the drain side selection gate SGD and the source sideselection gate SGS is, for example, thicker than one electrode layer WL.For example, a plurality of the drain side selection gates SGD and aplurality of the source side selection gates SGS may be provided. Thethickness of the drain side selection gate SGD and the source sideselection gate SGS may be equal to or thinner than the thickness of oneelectrode layer WL. In this case, as described above, the drain sideselection gate SGD and the source side selection gate SGS may beprovided in a plurality. Here, the term “thickness” used herein refersto the thickness in the stacking direction (Z-direction) of the stackedbody 15.

In the stacked body 15, columnar section CL extending in the Z-directionis provided. The columnar section CL pierces through the stacked body15. The columnar section CL is formed in, for example, a columnar orelliptic columnar shape. The columnar section CL is electricallyconnected to the conductive layer 60.

In the stacked body 15, groove ST piercing through the stacked body 15and extending in the X-axis direction are provided. Source layer SL isprovided in the groove ST. Side surface of the source layer SL iscovered by insulating film 44. Like the groove ST, the source layer SLextends in the X-axis direction. As the source layer SL, a materialhaving electric conductivity (e.g., tungsten) is used.

The lower end of the source layer SL is electrically connected tochannel body 20 (semiconductor body) of the columnar section CL via theconductive layer 60. The upper end of the source layer SL iselectrically connected to a not-shown control circuit.

For example, the source layer SL may be provided between the substrate10 and the conductive layer 60. In this case, not-shown contact layer isprovided in the groove ST. The source layer SL is electrically connectedto the control circuit via the contact layer. The insulating layer 44may be embedded in the groove ST.

FIG. 3 is an enlarged schematic sectional view of a part of the columnarsection CL in the embodiment.

The columnar section CL is formed in a memory hole formed in the stackedbody 15 including the plurality of electrode layers WL and the pluralityof interlayer insulating layers 40. The channel body 20 functioning assemiconductor channels is provided in the memory hole. The channel body20 is, for example, silicon film including silicon as a main component.

The channel body 20 is provided in a cylindrical shape extending in thestacking direction of the stacked body 15. The upper end of the channelbody 20 is connected to bit line BL (interconnects) shown in FIG. 1. Thelower end side of the channel body 20 is connected to the conductivelayer 60. The bit line BL extends in the Y-direction.

Memory film 30 is provided between the electrode layer WL and thechannel body 20. The memory film 30 include block insulating film 35,charge storage film 32, and tunnel insulating film 31.

The block insulating film 35, the charge storage film 32, and the tunnelinsulating film 31 are provided in order from the electrode layer WLside between the electrode layer WL and the channel body 20. The blockinsulating film 35 is in contact with the electrode layer WL. The tunnelinsulating film 31 is in contact with the channel body 20. The chargestorage film 32 is provided between the block insulating film 35 and thetunnel insulating film 31.

The electrode layer WL surrounds the channel body 20 via the memory film30. A core insulating film 50 is provided on the inner side of thechannel body 20.

The channel body 20 functions as channel in memory cells. The electrodelayer WL functions as control gate of the memory cells. The chargestorage film 32 functions as data memory layer that stores chargesinjected from the channel body 20. That is, memory cells havingstructure in which the control gate surrounds the channel is formed incrossing portion of the channel body 20 and the electrode layer WL.

As shown in FIG. 2A, an insulating layer 43 is provided on the drainside selection gate SGD. The bit line BL is provided on the insulatinglayer 43. The bit line BL is connected to the upper end of the channelbody 20 via contact plug CN piercing through the insulating layer 43.The upper end of the source layer SL is connected to not-shown sourceinterconnects.

A semiconductor memory device in the embodiment can electrically freelyperform erasing and writing of data and can retain stored contents evenif a power supply is turned off.

The memory cell is, for example, a charge trap type. The charge storagefilm 32 includes a large number of trap sites for capturing charges andis silicon nitride film, for example.

The tunnel insulating film 31 functions as potential barrier whencharges are injected to the charge storage film 32 from the channel body20 or when charges stored in the charge storage film 32 diffuse to thechannel bodies 20. The tunnel insulating films 31 are, for example,silicon oxide films.

As the tunnel insulting film 31, laminated film (ONO film) formed bysandwiching a silicon nitride film with a pair of silicon oxide filmsmay be used. When the ONO film is used as the tunnel insulating film 31,it is possible to perform an erasing operation in a low electric fieldcompared with a single layer of a silicon oxide film.

The block insulating film 35 prevents the charges stored in the chargestorage film 32 from diffusing to the electrode layer WL. The blockinsulating film 35 includes cap film 34 provided in contact with theelectrode layer WL and block film 33 provided between the cap film 34and the charge storage film 32.

The block film 33 is, for example, silicon oxide films. The cap film 34is a film having a dielectric constant higher than the dielectricconstant of silicon oxide and is, for example, at least one of siliconnitride film and aluminum oxide. By providing the cap film 34 in contactwith the electrode layer WL, it is possible to suppress back tunnelingelectron injected from the electrode layer WL during erasing. That is,by using laminated film of silicon oxide film and silicon nitride filmas the block insulating film 35, it is possible to improve a chargeblocking property.

As shown in FIG. 1, drain side selection transistor STD is provided atthe upper end portion of the columnar section CL in the memory stringMS. A source side selection transistor STS is provided at the lower endportion of the columnar section CL in the memory string MS.

The memory cells, the drain side selection transistor STD, and thesource side selection transistor STS are vertical transistors in whichan electric current flows in the stacking direction of the stacked body15 (the Z-direction).

The drain side selection gate SGD functions as a gate electrode (acontrol gate) of the drain side selection transistor STD. Insulatingfilm functioning as gate insulating film of the drain side selectiontransistor STD is provided between the drain side selection gate SGD andthe channel body 20.

The source side selection gate SGS functions as a gate electrode (acontrol gate) of the source side selection transistor STS. Insulatingfilm functioning as gate insulating films of the source side selectiontransistor STS is provided between the source side selection gate SGSand the channel body 20.

A plurality of memory cells having the respective electrode layers WL ascontrol gates are provided between the drain side selection transistorSTD and the source side selection transistor STS.

The plurality of memory cells, the drain side selection transistor STD,and the source side selection transistor STS are connected in seriesthrough the channel body 20 and configure one memory string MS. Aplurality of the memory strings MS are arrayed in the X-direction andthe Y-direction, whereby the plurality of memory cells arethree-dimensionally provided in the X-direction, the Y-direction, andthe Z-direction.

As shown in FIG. 2A, on the substrate 10, the conductive layer 60 andthe insulating layer 42 are provided via the insulating layer 41. Theconductive layer 60 is provided in the insulating layer 42. Theconductive layer 60 includes first films 61, second films 62, and airgap 60 s.

As the first film 61, for example, polysilicon film is used and n-typepolysilicon doped with arsenic or the like is used. As the second film62, for example, tungsten is used.

The first film 61 is provided on side surface side of the conductivelayer 60. The second film 62 is provided on the inner side of the firstfilm 61. The air gap 60 s is provided on the inner side of the secondfilm 62 and is entirely surrounded and covered by the second film 62.

Lower end portion 20 u of the channel body 20 projects to the conductivelayer 60. The lower end portion 20 u of the channel body 20 has end face(bottom surface) and side surface not covered by the memory film 30.That is, the lower end portion of the columnar section CL is formed in awedge shape having the channel body 20 as the distal end.

The lower end portion 20 u of the channel body 20 is in contact with thefirst film 61. The lower end portion 20 u of the channel body 20 iscovered by the first film 61 and covered by the second film 62 via thefirst film 61. That is, the channel body 20 is electrically connected tothe first film 61 and the second film 62 via the lower end portion 20 u.

According to the embodiment, the channel body 20 is in contact with theconductive layer 60 not only on the end face (the bottom surface) of thelower end portion 20 u but also on the side surface. Therefore, the areaof the channel body 20 in contact with the conductive layer 60 is largeand contact resistance decreases.

For example, the conductive layer 60 may include first barrier film 63and second barrier film 64 (FIGS. 13A and 13B). The first barrier film63 is formed between the first film 61 and the second film 62. Thesecond barrier film 64 is formed between the first barrier film 63 andthe second film 62.

As the first barrier film 63, for example, titanium film is used. As thesecond barrier film 64, for example, titanium nitride film is used.Consequently, it is possible to reduce contact resistance of the firstfilm 61 and the second film 62.

The source layer SL is provided in the groove ST. The source layer SLincludes the first film 61 (third film) and the second film 62 (fourthfilm). That is, as the source layer SL, a material same as the materialof the conductive layer 60 is used.

The first film 61 is provided on the side surfaces of the source layerSL and extends in the stacking direction piercing through the stackedbody 15. The second film 62 is provided on the inner side of the firstfilm 61. The first film 61 and the second film 62 of the source layer SLare integrally connected to the conductive layer 60.

The insulating film 44 is provided between the side surfaces of thesource layer SL and the electrode layer WL of the stacked body 15.Consequently, the source layer SL is not short-circuited with theelectrode layer WL. The insulating film 44 is also provided between thesource side selection gate SGS and the source layer SL and between thedrain side selection gate SGD and the source layer SL.

The first film 61 and the second film 62 are integrally provided inregion where the source layer SL and the conductive layer 60 are formed.In region where the slit-like source layer SL is formed, the first film61 and the second film 62 are provided in order from the side surfaceside.

The insulating layer 42 includes the column 65. As shown in FIG. 2A, thecolumn 65 is provided on the substrate 10 via the insulating layer 41.The side surface of the conductive layer 60 is in contact with thecolumn 65.

The side surface of the column 65 is covered by the conductive layer 60.The column 65 is provided integrally within an insulating layer 42 onthe column 65.

The stacked body 15 is provided on the conductive layer 60 and thecolumn 65 via the insulating layer 42. As described below, a sacrificiallayer 55 is once formed in region where the conductive layer 60 isformed (FIG. 4A). After the stacked body 15 is formed on the sacrificiallayer 55, the sacrificial layer 55 is removed. When the sacrificiallayer 55 is removed, the column 65 supports the stacked body 15.

According to the embodiment, it is possible to realize reliabilityimprovement and refining of the memory cell. Further, it is possible torealize a reduction in a block size and an increase in an electriccurrent. It is possible to perform a high-speed operation.

A method for manufacturing the semiconductor memory device in theembodiment is described with reference to FIGS. 4A to 13B.

FIGS. 4A, 5A, 6A, 7A, 8A, 9A, 10A, 11A, 12A, and 13A are schematicsectional views. FIGS. 4B, 5B, 6B, 7B, 8B, 9B, 10B, 11B, 12B, and 13Bare schematic top views of the schematic sectional views.

As shown in FIG. 4A, the insulating layer 41 is formed on the substrate10. The sacrificial layer 55 is formed on the insulating layer 41. Holes65 h are formed in the sacrificial layer 55. The holes 65 h piercethrough the sacrificial layer 55.

In a process described below, the sacrificial layer 55 is removed. Theconductive layers 60 are formed in portions where the sacrificial layer55 is removed (a replacing process). As the sacrificial layer 55, forexample, at least one of amorphous silicon and a silicon nitride film isused.

As shown in FIG. 5A, insulating films are embedded in the holes 65 h.Consequently, the columns 65 are formed. The sacrificial layer 55 issurrounded and covered by the insulating layer 42. Thereafter, thesource side selection gate SGS is formed on the sacrificial layer 55 andthe columns 65 via the insulating layer 42. On the source side selectiongate SGS, the stacked body 15 in which the interlayer insulating layers40 and the electrode layers WL are alternately stacked is formed. Thedrain side selection gate SGD is formed on the top electrode layer WLvia the interlayer insulating layer 40. The insulating layer 43 isformed on the drain side selection gate SGD.

Thereafter, a plurality of memory holes MH are formed in the stackedbody. The memory holes MH are formed by, for example, an RIE method(Reactive Ion Etching) using a not-shown mask. The memory holes MHpierce through the insulating layer 43 to the insulating layer 42 toreach the sacrificial layer 55.

After the memory holes MH are formed, the films (the memory films 30 andthe films including the channel bodies 20) shown in FIG. 3 are formed inorder on the inner walls (the sidewalls and the bottoms) of the memoryholes MH. Thereafter, the respective films formed on the insulatinglayers 42 are removed. Consequently, as shown in FIG. 6A, the columnarsections CL are formed.

In this case, the lower end portions 20 u of the channel bodies 20project to the sacrificial layer 55 and are covered by the memory films30. The memory films 30 that cover the lower end portions 20 u of thechannel bodies 20 are covered by the sacrificial layer 55.

For example, as shown in FIG. 6B, the columnar sections CL are formed tosurround the columns 65. The arrangement of the columnar sections CL isarbitrary. The columnar sections CL may overlap the columns 65.

As shown in FIG. 7A, the grooves ST piercing through the insulatinglayer 43 to the insulating layer 42 to reach the sacrificial layer 55are formed in the stacked body 15. As shown in FIG. 7B, the grooves STextend in the X-axis direction and divide the stacked body 15. Thesacrificial layer 55 is exposed on the bottom surfaces of the groovesST.

As shown in FIG. 8A, the insulating films 44 are formed on the sidewallsof the grooves ST. The insulating films 44 formed on the bottoms of thegrooves ST are removed. Consequently, the side surfaces of the sourceside selection gate SGS, the stacked body 15, and the drain sideselection gate SGD exposed on the sidewalls of the grooves ST arecovered by the insulating layer 43.

As shown in FIG. 9A, the sacrificial layer 55 is removed by, forexample, wet etching through the grooves ST. Consequently, hollows 55 hare formed under the stacked body 15.

The hollows 55 h are connected to the grooves ST. The lower end portions20 u of the channel bodies 20 project to the hollows 55 h and arecovered by the memory films 30. The memory films 30 that cover the lowerend portions 20 u of the channel bodies 20 are exposed to the hollows 55h.

In this case, the stacked body 15 is supported by the columns 65 formedamong the hollows 55 h.

As shown in FIG. 10A, the memory films 30 exposed to the hollows 55 hare removed by, for example, the wet etching through the grooves ST.Consequently, the lower end portions 20 u of the channel bodies 20projecting to the hollows 55 h are exposed to the hollows 55 h withoutbeing covered by the memory films 30.

Thereafter, as shown in FIG. 11A, the first films 61 having electricconductivity are formed on the inner walls of the hollows 55 h and thesidewalls of the grooves ST. The first films 61 are integrally formed onthe inner walls of the hollows 55 h and the sidewalls of the grooves ST.That is, the same first films 61 are formed on the sidewalls of thegrooves ST and the inner walls of the hollows 55 h.

The lower end portions 20 u of the channel bodies 20 projecting to thehollows 55 h are covered by the first films 61. The first films 61 areconformally formed along the end faces (bottom surfaces) and the sidesurfaces of the lower end portions 20 u. As the first films 61, forexample, polysilicon films are used.

As shown in FIG. 12A, the second films 62 are formed in the hollows 55 hand the grooves ST. The second films 62 cover the lower end portions 20u of the channel bodies 20 via the first films 61. Consequently, theconductive layers 60 and the source layers SL are formed.

In the conductive layers 60, the air gaps 60 s are formed. The air gaps60 s are entirely covered by the second films 62. The air gaps 60 s arenot in contact with the lower end portions 20 u of the channel bodies20.

For example, as shown in FIG. 13A, the first barrier films 63 and thesecond barrier films 64 may be formed between the first films 61 and thesecond films 62.

The first barrier films 63 are formed between the first films 61 and thesecond films 62. The second barrier films 64 are formed between thefirst barrier films 63 and the second films 62.

As the first barrier films 63, for example, titanium films are used. Asthe second barrier films 64, for example, titanium nitride films areused.

As shown in FIG. 2A, the contact plugs CN piercing through theinsulating layer 43 to reach the columnar sections CL are formed.

Thereafter, the bit lines BL, source interconnects, and the like areformed. Consequently, the semiconductor memory device in the embodimentis obtained.

According to the embodiment, the conductive layers 60 are formed by thereplacing process using the sacrificial layer 55. Consequently, it ispossible to etch only the memory films 30 formed on the bottom surfacesof the columnar sections CL. Therefore, the memory films 30 of thememory cells formed above the lower end portions 20 u of the channelbodies 20 are not affected by the etching. Therefore, it is possible tosuppress characteristic fluctuation and deterioration of the memorycells. Further, it is possible to realize a reduction in a block sizeand an increase in an electric current. It is possible to perform ahigh-speed operation.

FIGS. 14A and 14B are schematic diagrams of a memory string in anotherembodiment. FIG. 14A is a schematic sectional view of the memory stringMS. FIG. 14B shows an upper surface parallel to the XY plane in FIG.14A.

According to the embodiment, as shown in FIG. 14A, the conductive layer60 is provided on the substrate 10 not via the insulating layer 41. Theconductive layer 60 includes crystal film 60 a. The conductive layer 60is provided in the insulating layer 42.

In the conductive layer 60, the crystal film 60 a is embedded and airgap is not provided. The crystal film 60 a is formed by an epitaxialgrowth method with, for example, silicon of the substrate 10 as cores.

The lower end portion 20 u of the channel body 20 is covered with thecrystal film 60 a. The channel body 20 is electrically connected to theconductive layer 60 via the lower end portion 20 u.

In the embodiment, as in the embodiment described above, the area of thechannel body 20 in contact with the conductive layer 60 is large andcontact resistance decreases.

The source layer SL in the groove ST includes the second film 62 (metalfilm). The second film 62 is embedded in the source layer SL. The secondfilm 62 is in contact with the crystal film 60 a of the conductive layer60 and electrically connected to the crystal film 60 a. Consequently,the channel body 20 is electrically connected to the source layer SL viathe conductive layer 60.

The insulating film 44 is provided between the side surface of thesource layer SL and the electrode layer WL of the stacked body 15.Consequently, the source layer SL is not short-circuited with theelectrode layer WL. The insulating film 44 is also provided between thesource side selection gate SGS and the source layer SL and between thedrain side selection gate SGD and the source layer SL.

According to the embodiment, as in the embodiment described above, it ispossible to realize reliability improvement and refining of the memorycells. Further, it is possible to realize a reduction in a block sizeand an increase in an electric current. It is possible to perform ahigh-speed operation.

A method for manufacturing the semiconductor memory device in the otherembodiment is described with reference to FIGS. 15A and 15B.

FIG. 15A is a schematic sectional view. FIG. 15B is a schematic top viewin FIG. 15A. In the embodiment, unlike FIG. 4A in the embodimentdescribed above, the sacrificial layer 55 is formed on the substrate 10not via the insulating layer 41. The holes 65 h are formed in thesacrificial layer 55. The holes 65 h pierce through the sacrificiallayer 55.

For example, the substrate 10 is formed in a recessed shape. Thesacrificial layer 55 is embedded in recessed sections of the substrate10. In this case, the holes 65 h are not formed in the sacrificial layer55. The outer sides of the recessed sections of the substrate 10 areformed as the columns 65.

Thereafter, a manufacturing method same as the manufacturing methodshown in FIGS. 5A to 10B in the embodiment described above is used.Therefore, explanation of the manufacturing method is omitted.

Insulating films are embedded in the holes 65 h. Consequently, thecolumns 65 are formed. The sacrificial layer 55 is surrounded andcovered by the insulating layer 42. Thereafter, the source sideselection gate SGS is formed on the sacrificial layer 55 and the columns65 via the insulating layer 42. The stacked body 15 in which theinterlayer insulating layers 40 and the electrode layers WL arealternately stacked is formed on the source side selection gate SGS. Thedrain side selection gate SGD is formed on the top electrode layer WLvia the interlayer insulating layer 40. The insulating layer 43 isformed on the drain side selection gate SGD.

Thereafter, the plurality of memory holes MH are formed in the stackedbody. The memory holes MH are formed by, for example, the RIE methodusing a not-shown mask. The memory holes MH pierce through theinsulating layer 43 to the insulating layer 42 to reach the sacrificiallayer 55.

After the memory holes MH are formed, the films (the memory films 30 andthe films including the channel bodies 20) shown in FIG. 3 are formed inorder on the inner walls (the side walls and the bottoms) of the memoryholes MH. Thereafter, the films formed on the insulating layer 42 areremoved. Consequently, the columnar sections CL are formed.

In this case, the lower end portions 20 u of the channel bodies 20project to the sacrificial layer 55 and are covered by the memory films30. The memory films 30 that cover the lower end portions 20 u of thechannel bodies 20 are covered by the sacrificial layer 55.

Subsequently, the grooves ST piercing through the insulating layer 43 tothe insulating layer 42 to reach the sacrificial layer 55 are formed inthe stacked body 15. The grooves ST extend in the X-axis direction anddivide the stacked body 15. The sacrificial layer 55 is exposed on thebottom surfaces of the grooves ST.

Thereafter, the insulating films 44 are formed on the sidewalls of thegrooves ST. The insulating films 44 formed on the bottoms of the groovesST are removed. Consequently, the side surfaces of the source sideselection gate SGS, the stacked body 15, and the drain side selectiongate SGD exposed on the sidewalls of the grooves ST are covered by theinsulating layer 43.

Subsequently, the sacrificial layer 55 is removed by, for example, thewet etching through the grooves ST. Consequently, the hollows 55 h areformed under the stacked body 15.

The hollows 55 h are connected to the grooves ST. The lower end portions20 u of the channel bodies 20 project to the hollows 55 h and arecovered by the memory films 30. The memory films 30 that cover the lowerend portions 20 u of the channel bodies 20 are exposed to the hollows 55h.

In this case, the stacked body 15 is supported by the columns 65 formedamong the hollows 55 h.

Subsequently, the memory films 30 exposed to the hollows 55 h areremoved by, for example, the wet etching through the grooves ST.Consequently, the lower end portions 20 u of the channel bodies 20projecting to the hollows 55 h are exposed to the hollows 55 h withoutbeing covered by the memory films 30.

Thereafter, as shown in FIG. 15A, the crystal films 60 a are embedded inthe inner walls of the hollows 55 h. The crystal films 60 a are formedby the epitaxial growth method with, for example, the silicon on theupper surface of the substrate 10 as cores. As the crystal films 60 a,for example, semiconductor crystal films (silicon films, silicongermanium films, etc.) are used.

The crystal films 60 a cover the lower end portions 20 u of the channelbodies 20 projecting to the hollows 55 h. The lower end portions 20 u ofthe channel bodies 20 are electrically connected to the crystal films 60a. Consequently, the conductive layers 60 are formed.

Thereafter, as shown in FIG. 14A, the second films 62 are formed in thegrooves ST. The second films 62 are formed on the inner sides of theinsulating films 44 and embed source layers. The bottom surfaces of thesecond films 62 are in contact with the crystal films 60 a andelectrically connected to the crystal films 60 a. Consequently, thesource layers SL are formed.

The source layers SL are electrically connected to the channel bodies 20via the conductive layers 60. The source layers SL are made of, forexample, a material different from the material of the crystal films 60a. Subsequently, the contact plugs CN piercing through the insulatinglayer 43 to reach the columnar sections CL are formed.

Thereafter, the bit lines BL, source interconnects, and the like areformed. Consequently, the semiconductor memory device in the embodimentis obtained.

According to the embodiment, as in the embodiment described above, thememory films 30 of the memory cells formed above the lower end portions20 u of the channel bodies 20 are not affected by the etching.Therefore, it is possible to suppress characteristic fluctuation anddeterioration of the memory cells. Further, it is possible to realize areduction in a block size and an increase in an electric current. It ispossible to perform a high-speed operation.

FIGS. 16A and 16B are schematic diagrams of a memory string in stillanother embodiment. FIG. 16A is a schematic sectional view of the memorystring MS. FIG. 16B shows an upper surface parallel to the XY plane inFIG. 16A.

According to the embodiment, as shown in FIG. 16A, the source layer SL(a metal layer) is provided on the substrate 10 via the insulating layer41 (first insulating layer). The conductive layer 60 and insulatinglayer 42 (second insulating layer) are provided on the source layer SL.The conductive layer 60 is provided in the insulating layer 42. Theconductive layer 60 includes the first film 61 and the air gap 60 s.

The first film 61 is provided on the side surface side of the conductivelayer 60. The air gap 60 s is provided on the inner side of the firstfilm 61 and is entirely surrounded and covered by the first film 61.

The lower end portion 20 u of the channel body 20 is covered by thefirst film 61. The channel body 20 is electrically connected to theconductive layer 60 via the lower end portion 20 u. Consequently, thechannel body 20 is electrically connected to the source layer SL via theconductive layer 60.

In the embodiment, as in the embodiment described above, the area of thechannel body 20 in contact with the conductive layer 60 is large andcontact resistance decreases.

The first film 61 is embedded in dividing section ST. The first film 61is integrally provided from the conductive layer 60 to the dividingsection ST. For example, insulating film may be embedded in the dividingsection ST.

The insulating film 44 is provided between the side surface of the firstfilm 61 of the dividing section ST and the electrode layer WL of thestacked body 15. Consequently, the first film 61 is not short-circuitedwith the electrode layer WL. The insulating film 44 is also providedbetween the source side selection gate SGS and the source layer SL andbetween the drain side selection gate SGD and the source layer SL.

According to the embodiment, as in the embodiment described above, it ispossible to realize reliability improvement and refining of the memorycells. Further, it is possible to realize a reduction in a block sizeand an increase in an electric current. It is possible to perform ahigh-speed operation.

Further, the source layer SL is provided under the conductive layer 60.Consequently, since it is unnecessary to provide the source layer SL inthe dividing section ST, it is possible to reduce the size of the memorycell array 1.

A method for manufacturing the semiconductor memory device according tostill another embodiment is described.

In the embodiment, unlike FIG. 4A in the embodiment described above, thesource layer SL is formed on the substrate 10 via the insulating layer41. As the source layer SL, for example, tungsten is used.

The sacrificial layer 55 is formed on the source layer SL. The holes 65h are formed in the sacrificial layer 55. The holes 65 h pierce throughthe sacrificial layer 55.

Thereafter, a manufacturing method same as the manufacturing methodshown in FIGS. 5A to 11B in the embodiment described above is used.Therefore, explanation of the manufacturing method is omitted.

Insulating films are embedded in the holes 65 h. Consequently, thecolumns 65 are formed. The sacrificial layer 55 is surrounded andcovered by the insulating layer 42. Thereafter, the source sideselection gate SGS is formed on the sacrificial layer 55 and the columns65 via the insulating layer 42. The stacked body 15 in which theinterlayer insulating layers 40 and the electrode layers WL arealternately stacked is formed on the source side selection gate SGS. Thedrain side selection gate SGD is formed on the top electrode layer WLvia the interlayer insulating layer 40. The insulating layer 43 isformed on the drain side selection gate SGD.

Thereafter, the plurality of memory holes MH are formed in the stackedbody. The memory holes MH are formed by, for example, the RIE methodusing a not-shown mask. The memory holes MH pierce through theinsulating layer 43 to the insulating layer 42 to reach the sacrificiallayer 55.

After the memory holes MH are formed, the films (the memory films 30 andthe films including the channel bodies 20) shown in FIG. 3 are formed inorder on the inner walls (the side walls and the bottoms) of the memoryholes MH. Thereafter, the films formed on the insulating layer 42 areremoved. Consequently, the columnar sections CL are formed.

In this case, the lower end portions 20 u of the channel bodies 20project to the sacrificial layer 55 and are covered by the memory films30. The memory films 30 that cover the lower end portions 20 u of thechannel bodies 20 are covered by the sacrificial layer 55.

Subsequently, the dividing sections ST piercing through the insulatinglayer 43 to the insulating layer 42 to reach the sacrificial layer 55are formed in the stacked body 15. The dividing sections ST extend inthe X-axis direction and divide the stacked body 15. The sacrificiallayer 55 is exposed on the bottom surfaces of the dividing sections ST.

Thereafter, the insulating films 44 are formed on the sidewalls of thedividing sections ST. The insulating films 44 formed on the bottoms ofthe dividing sections ST are removed. Consequently, the side surfaces ofthe source side selection gate SGS, the stacked body 15, and the drainside selection gate SGD exposed on the sidewalls of the dividingsections ST are covered by the insulating layer 43.

Subsequently, the sacrificial layer 55 is removed by, for example, thewet etching through the dividing sections ST. Consequently, the hollows55 h are formed under the stacked body 15.

The hollows 55 h are connected to the dividing sections ST. The lowerend portions 20 u of the channel bodies 20 project to the hollows 55 hand are covered by the memory films 30. The memory films 30 that coverthe lower end portions 20 u of the channel bodies 20 are exposed to thehollows 55 h.

In this case, the stacked body 15 is supported by the columns 65 formedamong the hollows 55 h.

Subsequently, the memory films 30 exposed to the hollows 55 h areremoved by, for example, the wet etching through the dividing sectionsST. Consequently, the lower end portions 20 u of the channel bodies 20projecting to the hollows 55 h are exposed to the hollows 55 h withoutbeing covered by the memory films 30.

Thereafter, as shown in FIG. 16A, the first films 61 having electricconductivity are formed on the inner walls of the hollows 55 h and thesidewalls of the dividing sections ST. the first films 61 are integrallyformed on the inner walls of the hollows 55 h and the sidewalls of thedividing sections ST. That is, the same first films 61 are formed on thesidewalls of the dividing sections ST and the inner walls of the hollows55 h. The first films 61 are embedded in the inner walls of the dividingsections ST.

The lower end portions 20 u of the channel bodies 20 projecting to thehollows 55 h are covered by the first films 61. The air gaps 60 s areformed on the inner sides of the first films 61. The air gaps 60 s areentirely surrounded and covered by the first films 61. The source layerSL is electrically connected to the channel bodies 20 via the conductivelayers 60.

Subsequently, the contact plugs CN piercing through the insulating layer43 to reach the columnar sections CL are formed. Thereafter, the bitlines BL, source interconnects, and the like are formed. Consequently,the semiconductor memory device in the embodiment is obtained.

According to the embodiment, as in the embodiment described above, thememory films 30 of the memory cells formed above the lower end portions20 u of the channel bodies 20 are not affected by the etching.Therefore, it is possible to suppress characteristic fluctuation anddeterioration of the memory cells. Further, it is possible to realize areduction in a block size and an increase in an electric current. It ispossible to perform a high-speed operation.

FIG. 18 is an enlarged schematic sectional view of a part of a columnarsection in another memory cell array in the embodiment.

A memory cell array 2 includes electrode layers WL2 and a columnarsection CL2 different from those of the memory cell array 1 describedabove. The memory cell array 2 is the same as the memory cell array 1except the electrode layers WL2 and the columnar section CL2. Therefore,explanation of the same components is omitted.

As shown in FIG. 18, the electrode layers WL2 include first metal layersWLa, second metal layers WLb, and cover layers WLc. As the first metallayer WLa and the second metal layer WLb, for example, tungsten is used.As the cover layer WLc, for example, titanium nitride is used.

The columnar section CL2 is formed in a memory hole formed in thestacked body 15 including a plurality of the electrode layers WL2 and aplurality of the interlayer insulating layers 40. In the memory hole,the channel bodies 20 functioning as semiconductor channels areprovided. The channel bodies 20 are, for example, silicon filmsincluding silicon as a main component.

The memory films 30 are provided between the electrode layers WL2 andthe channel bodies 20. The memory films 30 include the block insulatingfilms 35, the charge storage films 32, and the tunnel insulating films31.

The block insulating films 35, the charge storage films 32, and thetunnel insulating films 31 are provided in order from the electrodelayer WL2 sides between the electrode layers WL2 and the channel bodies20. The block insulating films 35 cover the electrode layers WL2. Thetunnel insulating films 31 are in contact with the channel bodies 20.The charge storage films 32 are provided between the block insulatingfilms 35 and the tunnel insulating films 31.

The electrode layers WL2 surround the channel bodies 20 via the memoryfilms 30. The core insulating film 50 is provided on the inner sides ofthe channel bodies 20.

The tunnel insulating films 31 are, for example, silicon oxide films.Alternatively, as the tunnel insulating films 31, laminated films (ONOfilms) formed by sandwiching a silicon nitride film with a pair ofsilicon oxide films may be used.

The block insulating films 35 include the cap films 34 that surround andcover the electrode layers WL2 and the block films 33 that cover theelectrode layers WL2 via the cap films 34. The block films 33 are, forexample, silicon oxide films. The cap films 34 are films having adielectric constant higher than the dielectric constant of the blockfilm 33 and are, for example, at least one of aluminum oxide and siliconnitride films. By providing the cap films 34 in contact with theelectrode layers WL2, it is possible to suppress back tunnelingelectrons injected from the electrode layers WL2 during erasing.

In the stacking direction, the block insulating films 35 are separatedvia the interlayer insulating layers 40.

In the memory cell array 2, as in the embodiment described above, it ispossible to realize reliability improvement and refining of the memorycells. Further, it is possible to realize a reduction in a block sizeand an increase in an electric current. It is possible to perform ahigh-speed operation.

A method for manufacturing the other memory cell array in the embodimentis described with reference to FIGS. 19 to 23.

FIGS. 19 to 23 are schematic sectional views of the memory string MS.

As shown in FIG. 19, sacrificial layers 56 and the interlayer insulatinglayers 40 are alternately stacked on the insulating layer 42. Note thatstructure below the insulating layer 42 is common to the structure in atleast any one of the manufacturing methods described above. Therefore,explanation of the structure is omitted.

As shown in FIG. 20, the columnar sections CL2 piercing through astacked body 16 in the stacking direction are formed. As shown in FIG.18, in the columnar section CL2, the charge storage films 32, the tunnelinsulating films 31, the channel bodies 20, and the core insulating film50 are formed in order from the outer side. In the columnar section CL2,for example, like the columnar section CL described above, the blockinsulating films 35 may be formed on the side surfaces of the chargestorage films 32.

As shown in FIG. 21, the insulating layer 43 is formed on the stackedbody 16. The grooves ST piercing through the stacked body 16 in thestacking direction are formed.

As shown in FIG. 22, the sacrificial layers 56 are removed through thegrooves ST to form hollows 56 h. As a method for removing thesacrificial layers 56, for example, a wet etching method is used. Inthis case, the stacked body 16 is supported by the columnar sectionsCL2.

As shown in FIG. 23, the block insulating films 35 (the block films 33and the cap films 34) are formed on the inner walls of the hollows 56 hthrough the grooves ST. Thereafter, on the inner sides of the blockinsulating films 35, the cover layers WLc, the second metal layers WLb,and the first metal layers WLa are formed and the electrode layers WL2are formed. Note that a method for forming a source side selection gateSGS2 and a drain side selection gate SGD2 is the same as the method forforming the electrode layers WL2. The source side selection gate SGS2 isformed under the stacked body 16. The drain side selection gate SGD2 isformed on the stacked body 16.

Thereafter, the semiconductor memory device in the embodiment includingthe memory cell array 2 is formed through processing same as theprocesses of the manufacturing method described above.

According to the embodiment, as in the embodiment described above, it ispossible to realize reliability improvement and refining of the memorycells. Further, it is possible to realize a reduction in a block sizeand an increase in an electric current. It is possible to perform ahigh-speed operation.

While certain embodiments have been described, these embodiments havebeen presented by way of example only, and are not intended to limit thescope of the inventions. Indeed, the novel embodiments described hereinmay be embodied in a variety of other forms; furthermore, variousomissions, substitutions and changes in the form of the embodimentsdescribed herein may be made without departing from the spirit of theinventions. The accompanying claims and their equivalents are intendedto cover such forms or modification as would fall within the scope andspirit of the inventions.

What is claimed is:
 1. A semiconductor memory device comprising: asubstrate; an insulating layer provided above the substrate; a stackedbody provided above the insulating layer and including a plurality ofelectrode layers separately stacked from each other in a firstdirection; at least three semiconductor bodies extending in the firstdirection through the stacked body and including lower end portionsbelow the stacked body; a memory portion provided between one of the atleast three semiconductor bodies and one of the plurality of electrodelayers; and a conductive layer including silicon and tungsten, providedbetween the insulating layer and the stacked body, and including atleast three portions electrically connected with the lower end portionsof the at least three semiconductor bodies respectively; the conductivelayer being not separated among the at least three portions.
 2. Thedevice according to claim 1, wherein the conductive layer extends in aplane crossing the first direction and is not separated among the atleast three portions in directions included in the plane.
 3. The deviceaccording to claim 1, further comprising: a plurality of bit lineselectrically connected to upper end portions of the at least threesemiconductor bodies respectively above the stacked body.
 4. The deviceaccording to claim 1, wherein one of the plurality of electrode layersadjacent to the conductive layer in the first direction is a source sideselection gate.
 5. The device according to claim 1, wherein the at leastthree semiconductor bodies include a first semiconductor body, a secondsemiconductor body, and a third semiconductor body, the firstsemiconductor body and the second semiconductor body being arranged in asecond direction crossing the first direction, the first semiconductorbody and the third semiconductor body being arranged in a thirddirection crossing the first direction and the second direction; andwherein the first semiconductor body, the second semiconductor body, andthe third semiconductor body are in contact with the conductive layer incommon via respective contact portions.
 6. The device according to claim1, wherein the conductive layer comprises a first conductive filmincluding polysilicon, and a second conductive film including tungsten.7. The device according to claim 6, wherein the first conductive film isin contact with the lower end portions of the at least threesemiconductor bodies.
 8. The device according to claim 7, wherein one ofthe plurality of electrode layers adjacent to the conductive layer inthe first direction is a source side selection gate, and the secondconductive film is provided below contact portions of the firstconductive film with the lower end portions of the at least threesemiconductor bodies and is not provided between the source sideselection gate and the contact portions of the first conductive film. 9.The device according to claim 1, further comprising: a plurality ofinsulating films extending in the first direction through the stackedbody to reach the conductive layer.
 10. The device according to claim 9,wherein the insulating films further extend in a second directioncrossing the first direction and a bit line extending direction, the bitline being electrically connected to an upper end portion of one of theat least three semiconductor bodies above the stacked body.
 11. Thedevice according to claim 1, further comprising: a source layer coupledto the at least three semiconductor bodies via the conductive layer, oneof the at least three semiconductor bodies being electricallyconnectable to the source layer via the conductive layer without via anyother one of the at least three semiconductor bodies.
 12. Asemiconductor memory device comprising: a substrate; an insulating layerprovided above the substrate; a stacked body provided above theinsulating layer and including a plurality of electrode layersseparately stacked from each other in a first direction; a plurality ofsemiconductor bodies extending in the first direction through thestacked body; a memory portion provided between one of the semiconductorbodies and one of the plurality of electrode layers; a conductive layerincluding silicon and tungsten, provided between the insulating layerand the stacked body, and including a plurality of portions electricallyconnected with lower end portions of the semiconductor bodiesrespectively below the stacked body; and a conductive material extendingin the first direction of which lower end is coupled to the conductivelayer, the semiconductor bodies being electrically connectable to theconductive material in common via the conductive layer.
 13. The deviceaccording to claim 12, wherein the semiconductor bodies include siliconand the conductive material includes tungsten.
 14. The device accordingto claim 12, wherein the conductive layer extends in a plane crossingthe first direction and is not separated in directions included in theplane among the portions electrically connected with lower end portionsof the semiconductor bodies respectively.
 15. The device according toclaim 12, further comprising: a plurality of bit lines electricallyconnected to upper end portions of the semiconductor bodies respectivelyabove the stacked body.
 16. The device according to claim 12, whereinone of the plurality of electrode layers adjacent to the conductivelayer in the first direction is a source side selection gate.
 17. Thedevice according to claim 12, wherein the semiconductor bodies include afirst semiconductor body, a second semiconductor body, and a thirdsemiconductor body, the first semiconductor body and the secondsemiconductor body being arranged in a second direction crossing thefirst direction, the first semiconductor body and the thirdsemiconductor body being arranged in a third direction crossing thefirst direction and the second direction; and wherein the firstsemiconductor body, the second semiconductor body, and the thirdsemiconductor body are in contact with the conductive layer in commonvia respective contact portions.
 18. The device according to claim 12,wherein the conductive layer comprises a first conductive film includingpolysilicon, and a second conductive film including tungsten.
 19. Thedevice according to claim 18, wherein the first conductive film is incontact with the lower end portions of the semiconductor bodies.
 20. Thedevice according to claim 19, wherein one of the plurality of electrodelayers adjacent to the conductive layer in the first direction is asource side selection gate, and the second conductive film is providedbelow contact portions of the first conductive film with the lower endportions of the semiconductor bodies and is not provided between thesource side selection gate and the contact portions of the firstconductive film.